1. Field of the Invention
The present invention relates to an optical compensation plate for a liquid crystal cell in which a distance of a liquid crystal layer is held through a spacer, a liquid crystal cell provided with the optical compensation plate, and a liquid crystal display device.
2. Description of the Related Art
Hitherto, as a liquid crystal display device in a VA (vertical alignment) mode, for example a transmissive liquid crystal display device, a reflective liquid crystal display device, and a semi-transmissive reflective liquid crystal display device have been proposed in Japanese Unexamined Patent Publication Nos. 11-242226 and 2001-209065. As an application of the liquid crystal display device in the VA mode, a liquid crystal television can be exemplified. Generally, a liquid crystal cell of the liquid crystal display device is provided with two liquid crystal cell substrates, spacers interposed between the two substrates, and a liquid crystal material filled into a gap between the two substrates. In the liquid crystal cell, a thickness (cell gap) of a liquid crystal layer, in which the liquid crystal material is filled, is kept constant through a spacer.
This liquid crystal layer, in which the liquid crystal material is filled, itself has a birefringent property and a retardation. An optical compensation plate capable of canceling (compensating) the retardation of the liquid crystal layer is laminated on the liquid crystal cell for improving a viewing angle characteristic resulting from this retardation.
As the optical compensation plate, for example, a biaxial optical film having a relationship of nx>ny>nz is known. This optical compensation plate is a film formed by, for example, applying a non-liquid crystal material selected from polyamide, polyimide, polyester, polyetherketone, polyamide-imide, polyesterimide and the like onto a transparent film typified by triacetyl cellulose, as described for example in Japanese Unexamined Patent Publication No. 2004-46065.
This optical compensation plate is formed so as to have a uniform thickness, and laminated on and bonded to, for example, the backlight side of the liquid crystal cell substrate.
However, even when the retardation of the liquid crystal layer is compensated by laminating the above-mentioned optical compensation plate, light leakage may occur in a central region of the liquid crystal cell. If the light leakage occurs, there is a problem that in viewing a liquid crystal display surface in a black-display state from an angle, the black-display level is deteriorated. Particularly in a relatively large liquid crystal cell, reduction in the black-display level in a central region of the display surface is apt to occur.